The broad, long term goal of this research is to improve the diagnosis and treatment of intracranial atherosclerotic disease (ICAD). The presence of intracranial atherosclerosis results in alterations in cerebral hemodynamics and also puts patients at risk for stroke. The prevalence of ICAD is known to increase with age indicating that is will be an increasing burden on healthcare cost with the aging of the population. Direct evaluation of tissue Oxygen Extraction Fraction (OEF) using positron emission tomography (PET) scans have provided direct insight into the severity, progression and risk of stroke in extra-cranial atherosclerosis (i.e. Carotid artery disease). Intracranial atherosclerosis induces a more focal loss of intracranial perfusion pressure and results in alterations in CBF, CBV, OEF. In this proposed work we will develop a new MRI pulse sequence for the quantification of OEF, verify its accuracy, reliability against PET.